// (define (fib n)
//    (if (< n 2) n (+ (fib (- n 1)) (fib (- n 2)))))

public class fib {
	public static void main(String [] args) {
            System.out.println(fib(Integer.parseInt(args[0])));
	}
	public static int fib(int n) {
		if (n<2)
			return n;
		else
			return fib(n-1)+fib(n-2);
	}
}